The present invention is related to a vertical restraint of the sort attached to a guide rail mounted on a floor of an aircraft cargo compartment.
One of the challenges confronting operators of freighter aircraft is efficiently handling cargo to be transported by the aircraft. Early freighters used manual labor to load and unload cargo. The loading and unloading operation has been improved dramatically by using large cargo containers designed to fit within the space limitations of an aircraft cargo compartment. Many items of freight headed for a single destination are loaded into a single container and then transported to the aircraft as a single unit rather than being transported as individual items of freight.
Aircraft cargo handling systems have been developed to move these cargo containers once they have been transported to the aircraft. For example, the cargo compartment deck surface may be equipped with ball bearing rollers to facilitate flight line workers moving pallets and containers resting on the rollers across the cargo deck surface manually. Some aircraft are equipped with powered mechanisms having friction rollers that provide the force to move the loaded cargo containers from the cargo compartment door to the place in the cargo compartment where they will be secured for the duration of the flight.
These powered cargo container handling systems require some means of guiding the heavy cargo containers to their proper destination in the cargo compartment, while preventing them from striking the side walls of the aircraft and possibly doing structural damage as they are being loaded or unloaded. Usually a system of stops serves to guide cargo containers and prevent them from striking aircraft side wall structure.
Because aircraft fuselages are not always the same width from the front of the cargo compartment to the rear, or because some cargo spaces in aircraft cargo compartments occupy less than the entire width of the aircraft, some cargo containers are wider than others. For a single cargo loading and unloading system to accommodate all widths of cargo containers, more than one set of cargo container guide stops may be required in the same area of the cargo compartment. Cargo containers of different widths are usually loaded in batches of a particular width until the area of the cargo compartment intended for receiving such cargo containers is full. When wide cargo containers are being loaded, the guide stops intended to accommodate narrower cargo containers are retracted into the cargo deck surface or removed so as not to interfere with passage of wider containers.
If a guide stop for narrow containers is inadvertently left in place, it is in danger of being struck by a heavily loaded cargo container when the loading operation switches to the wider containers. When struck directly by a fully loaded cargo container weighing several thousand pounds, and especially if propelled by a powered roller system, these stops themselves can be damaged, but more importantly, can transmit the impact force to the cargo deck surface to which they are attached, damaging it as well. Damage to the cargo container (and sometimes, to the cargo therein) can occur as a result of such forceful contact.
Air cargo operators need a means of guiding such cargo containers that will reliably guide the containers to their proper locations in the cargo compartment, but that will not transmit damaging forces to the cargo deck surface if accidentally struck directly by a heavy cargo container.
U.S. Pat. No. 5,692,862 shows a cargo system suitable for this purpose. FIG. 1A, taken from FIG. 1 of the '862 patent, shows a guide rail and support assembly 10 with its longitudinal axis 2a parallel with the preferred direction of cargo container movement 1. Guide rail and support assembly 10 is comprised of a plurality of retracting rail supports 11a, 11b, and 11c. Of course, any number of retracting rail supports could be used, depending upon the desired length of guide rail and support assembly 10. Guide rail 13 links together the retracting rail supports 11a, 11b and 11c.
Guide rail and support assembly 10 typically has a rail end fitting 12 at each end to serve as a bumper to absorb impact from collisions with cargo containers, and to regain guidance of cargo containers as the cargo containers pass from one guide rail to the next. Also mounted on guide rail and support assembly 10 are a plurality of vertical restraints 14, one positioned at each retracting rail support position. The function of vertical restraint 14 is to allow cargo containers being transported across the cargo deck surface of an aircraft to pass by vertical restraint 14 in either direction along guide rail 13, but to be restrained from moving in the vertical direction. Vertical restraint 14 engages a recess on the cargo container to restrain it from moving vertically, but does not restrain it from moving horizontally. Vertical restraint 14 pivots in either the clockwise or counterclockwise directions to avoid restraining horizontal movement.
FIG. 1B shows an exploded view of a prior art vertical restraint and guide rail assembly. As seen in FIG. 1B, the vertical restraint and guide rail assembly includes a vertical restraint support bracket 22, sometimes referred to in the industry as a ‘rail fitting’. The prior art vertical restraint support bracket 22 comprises a handle member 24 configured to connect to a retracting rail support, a housing 26 provided with a compartment 28, and support wings 30A, 30B for securing the vertical restraint support bracket 22 to the guide rail 13.
The guide rail 13 comprises an upper leg 40A, a lower leg 40B and a cross-member 40C connecting the two. The guide rail 13 has an upper cutout 42A in the upper leg 40A that is centered over a larger, lower cutout 42B formed in the lower leg 40B. Bolts 70 are used in conjunction with washers 72 and nuts 74 to secure the vertical restraint support bracket 22 to the guide rail 13.
The vertical restraint assembly 44 includes a vertical restraint member 14, a leaf spring 50, a spacer member 52, a washer 54 and threaded bolt 56. These items are partially, or wholly, received into a bore 28. The upper portion of the bore 28 has a first, larger diameter, and the lower portion of the bore comprises a tapped hole into which the threaded end of the threaded bolt 56 is inserted. An annular ledge is present between the upper portion of the bore 28 and the lower portion. A spring pin is inserted into a hole formed in the ledge. This spring pin serves as an abutment against which facing edges of the leaf spring 50 abut, when the vertical restraint member 14 is in the neutral position. The vertical restraint member 14 has a downwardly extending arm (not shown) descending from a portion of its front flipper. When the vertical restraint member 14 is rotated in either direction, this downwardly extending arm abuts one or the other of the facing edges of the leaf spring 50, and forces apart the edges, thereby creating a resisting force that tends to return the vertical restraint member 14 to its original, neutral position.